Most 2,000 person office buildings have security guards and doors/gates/turnstiles that won’t let just anyone waltz in.
I did it accidentally once at a big hedge fund sort of company. I thought I was being escorted by my friend’s friend. But it was actually just some one familiar with them/their names not fully understanding what I was saying letting me thru the ~3? Times a badge scan was required. I wasn’t paying attention. Only when my friend got scared he would get in trouble did I realize what had happened.